[PATCH] aarch64: Avoid alloca in target attribute parsing

[Richard Sandiford]

The handling of the target attribute used alloca to allocate
a copy of unverified user input, which could exhaust the stack
if the input is too long.  This patch converts it to auto_vecs
instead.

I wondered about converting it to use std::string, which we
already use elsewhere, but that would be more invasive and
controversial.

I'll push tomorrow evening UK time if there are no comments
in the meantime.

Richard


gcc/
        * config/aarch64/aarch64.cc (aarch64_process_one_target_attr)
        (aarch64_process_target_attr): Avoid alloca.
---
 gcc/config/aarch64/aarch64.cc | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 7f0cc47d0f0..0d41a193ec1 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -19405,8 +19405,10 @@ aarch64_process_one_target_attr (char *arg_str)
       return false;
     }
 
-  char *str_to_check = (char *) alloca (len + 1);
-  strcpy (str_to_check, arg_str);
+  auto_vec<char, 32> buffer;
+  buffer.safe_grow (len + 1);
+  char *str_to_check = buffer.address ();
+  memcpy (str_to_check, arg_str, len + 1);
 
   /* We have something like __attribute__ ((target ("+fp+nosimd"))).
      It is easier to detect and handle it explicitly here rather than going
@@ -19569,8 +19571,10 @@ aarch64_process_target_attr (tree args)
     }
 
   size_t len = strlen (TREE_STRING_POINTER (args));
-  char *str_to_check = (char *) alloca (len + 1);
-  strcpy (str_to_check, TREE_STRING_POINTER (args));
+  auto_vec<char, 32> buffer;
+  buffer.safe_grow (len + 1);
+  char *str_to_check = buffer.address ();
+  memcpy (str_to_check, TREE_STRING_POINTER (args), len + 1);
 
   if (len == 0)
     {
-- 
2.25.1